Self-supporting capacitor structure

ABSTRACT

A plurality of high capacitance capacitors are coupled to supply or accept large currents. Bus bars are welded to the capacitors to provide improved thermal performance as well as self-supporting rigidity to the geometrical structure formed by the capacitors and the bus bars.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. application Ser. No. 10/960,034filed Oct. 7, 2004 and entitled “Self-Supporting Capacitor Structure”(the '034 application), now pending, which claims the benefit of U.S.provisional application Ser. No. 60/525,483, filed Nov. 26, 2003 (the'483 application) and U.S. provisional application No. 60/518,422 filedNov. 7, 2003 (the '422 application). The '034 application, the '483application, and the '422 application are each hereby incorporated byreference as though fully set forth herein.

FIELD OF THE INVENTION

The present invention is related to interconnections made to capacitorsin general, and to welded interconnections made to capacitors moreparticularly.

BACKGROUND

Known configurations for interconnection to capacitors include leads,tabs, and the like. Types of capacitor technology that useinterconnections include ceramic capacitors, electrolytic capacitors,and other types that are know to those skilled in the art. Knowncapacitor interconnections utilize both radial and axial configurations.When current flow through such capacitors is small, the interconnectionsneed not be large in diameter or cross-sectional area. Use of smallgeometrical sizes is allowed when maximum current is small.

Double-layer capacitors (also known as ultracapacitors andsupercapacitors) can now be produced as individual capacitors and arecapable of storing hundreds and thousands of farads in a single cell.Due in part to their large capacitance, double-layer capacitors cansupply or accept large currents. However, single double-layer capacitorcells are limited by physics and chemistry to a maximum operatingvoltage of about 4 volts, and nominally to about between 2.5 to 3 volts.As higher capacitance double-layer capacitors are configured for use inincreasingly higher voltage applications, even higher currents may begenerated during charge and discharge of the capacitors.

What is needed, therefore, are reliable interconnections andmethodologies for handling high current using double-layer capacitors.

SUMMARY

High capacitance capacitors can store large amounts of energy and arecapable of supplying or accepting large currents. As current flowthrough a capacitor increases, heat may be generated. Above a certainthreshold temperature or current, a capacitor may fail. The presentinvention addresses capacitor's tendency to fail at higher currentsand/or higher temperatures.

In one embodiment, a capacitor-based system comprises at least threedouble-layer capacitors, the capacitors comprising terminals throughwhich a high current may flow safely; and at least two bus bars, eachbus bar comprising two attachment points, wherein at the two attachmentpoints a double-layer capacitor and the bus bar form an integralstructure which passes the high current. The high current may be greaterthan 2000 amps. The at least one bus bar may comprise a relativelyductile metal. The system may comprise a vehicle, the vehicle comprisingan electrical device, wherein two of the terminals are coupled to theelectrical device. The at least three capacitors may be interconnectedin series and provide about 42 volts when charged. The at least threedouble-layer capacitors may be connected in series by the at least twobus bars. The bus bar may comprise an increased surface area. Theincreased surface area may comprise one or more rib. Between terminalsof the at least three capacitors may be interconnected two capacitorbalancing circuits. The least three capacitors and the at least two busbars may comprise a self supporting-structure. The self-supportingstructure may comprise welds. The welds may be laser welds. The weldsmay be ultrasonic welds. The welds may be cold formed. The two terminalsmay be disposed along one axis of each double layer capacitor. Theterminals and the at least two bus bars may comprise the same metal.

In one embodiment, a method of using a plurality of capacitors,comprises the steps of: providing a first and a second double-layercapacitor; providing a first bus bar; and welding a first end of thefirst bus bar to the first double-layer capacitor to form aself-supporting structure; and welding a second end of the first bus barto the second double-layer capacitor to form the self-supportingstructure. The method may also comprise the step of passing a current ofat least 250 amps through the first bus bar. The method may furtherprovide a third double-layer capacitor; provide a second bus bar; andweld a first end of the second bus bar to the third capacitor to formthe self-supporting structure; and weld a second end of the bus bar tothe second capacitor to form the self-supporting structure. The methodmay also comprise the steps of: providing an electrical device; andcoupling the double-layer capacitors to the electrical device to passcurrent between the capacitors and the electrical device. The electricaldevice may comprise a propulsion engine. The first and second capacitorsmay be connected by the bus bar in series. The self-supportingstructures may be oriented in any orientation.

In one embodiment, a capacitor structure may comprise a plurality ofcapacitors; and a plurality of bus bars for carrying a current betweenthe plurality of capacitors, wherein the plurality of bus bars and theplurality of capacitors form an integrally interconnectedself-supporting structure. The one or more of the bus bars may comprisean increased surface area. The bus bars may be welded to the pluralityof capacitors. The current may more than 250 amps. The capacitors may bedouble-layer capacitors. The capacitors may comprise terminals and theintegral interconnected structure may be comprised of the bus bars andthe terminals. The capacitors may comprise an aluminum housing andaluminum lid, wherein the housing and lid each comprise a terminal. Theself-supporting structure may include at least one capacitor balancingcircuit connected between two of the capacitors.

In one embodiment, a capacitor based system comprises at least twodouble-layer capacitors, the capacitors having axially disposedterminals through which current may flow safely; and at least one busbar, the bus bar comprising two attachment points, the at least one busbar for carrying the current between the double-layer capacitors, the atleast one bus bar welded at the two attachment points to respectiveterminals of the double-layer capacitors. The at least one bus bar maycomprise at least one void within which one of the terminals isdisposed.

Other embodiments, benefits, and advantages will become apparent upon afurther reading of the following Figures, Description, and Claims.

FIGURES

In FIG. 1 a there are seen capacitors connected in series.

In FIG. 1 b there is seen a structure of a double-layer capacitor.

In FIG. 2 there are illustrated capacitor current vs. capacitortemperature curves.

In FIG. 3 there are seen interconnections provided with increasedsurface area.

In FIG. 4 there is seen use of a cell balancing circuit.

In FIG. 5 there is seen a capacitor housing configured to provide anincreased surface area.

In FIG. 6 there are seen three views of six series interconnectedcapacitors.

In FIG. 7 there are seen three views of six series interconnectedcapacitors disposed within a container.

DESCRIPTION

High capacitance capacitors can store large amounts of energy and arecapable of supplying or accepting large currents. As current flowthrough a capacitor increases, heat may be generated. Above a certainthreshold temperature or current, a capacitor may fail. The presentinvention addresses the tendency of capacitors to fail at highercurrents and/or higher temperatures.

Referring now to FIG. 1 a, there are seen capacitors connected inseries. In one embodiment, four 2600 F |2.5 V|60 mm×172 mm|525 g| sealedcapacitors 12, 14, 16, 18 are interconnected as a series string ofcapacitors. A type of capacitor capable of such high capacitance isknown to those skilled in the art as a double-layer capacitor, oralternatively, as a supercapacitor or an ultracapacitor. In FIG. 1 a,the series string is formed using electrically conductiveinterconnections 30. Interconnections 30 connect a negative terminal ofa first capacitor 12 to a positive terminal of a second capacitor 14, anegative terminal of the second capacitor to a positive terminal of athird capacitor 16, and a negative terminal of the third capacitor 16 toa positive terminal 22 of a fourth capacitor 18. When a charging source20 is connected across the positive terminal of capacitor 12 and thenegative terminal of capacitor 18, a current flows through thecapacitors and the interconnections therebetween. In one embodiment, ithas been identified that when charged to 10 volts, over 2000 amps ofinstantaneous peak current may flow through the capacitors 12, 14, 16,18, and interconnections 30. Those skilled in the art will identify thatsuch peak current would be dependent on the particular application.

Referring to FIG. 1 b, and other Figures as needed, there is seen across-sectional view of a double-layer capacitor. In one embodiment, anot to scale representation of a double-layer capacitor 18 illustrates athermally and electrically conductive cylindrical housing 23, at leastone electrically conductive lid 29 for sealing the housing at an end, anelectrically insulative sealing portion 25 disposed between the lid 29and the housing 23, and an electrolyte impregnated capacitor cell 27comprised of double-layer capacitor technology known to those skilled inthe art, connected to, and disposed within, the sealed housing. In oneembodiment, capacitor cell 27 comprises a jelly-roll type configurationknown to those skilled in the art, wherein alternating rolled collectorsare electrically coupled either to the lid 29 and the housing 23. Thoseskilled in the art will identify that when an energy source or load iselectrically connected to terminals 22, 24, current may flow between thesource/load and through the capacitor 18. In one embodiment, in order tosafely handle high peak current flows of about 2000 amps through thecapacitor 18, as well to provide a structure that can be welded withoutdamage, the housing 23 is sized to be about 5.25 inches in length and2.25 inches in diameter, and the lid 29 is sized to be about 2.25 inchesin diameter. In one embodiment, the wall thickness of the cylindricalportion of the housing 23 is about 1/16 inch, and a wall thickness of abottom end portion of the housing used to connect to collectors of thecell 27 is about ⅜ inch thick. As well, a thickness of the lid 29 usedto connect to the collectors of the cell 27 is about ⅜ inch. In oneembodiment, the terminals 22, 24 are ⅝ inch in diameter and ⅞ inch inlength. In one embodiment, one or both the terminals 22, 24 are formedat the time of manufacture of the lid 29 and housing 23, for example, bycold forming, extrusion, etc., or other techniques used for formingintegral structures that are known to those skilled in the art.

In FIG. 1 a there is also seen that across respective positive andnegative terminals of the capacitor 12 and 14, and across respectivepositive and negative terminals of the capacitor 14 and 16, and acrossrespective positive and negative terminals of the capacitor 16 and 18, arespective cell balancing circuit 32, 33, 35 is connected. A detaileddescription of connection, operation, and use of cell balancing circuitsis discussed in commonly assigned patent application Ser. No.10/423,708, filed 25 Apr. 2003, which is incorporated herein byreference. Because the current used by the cell balancing circuits 32,33, 35 may be low, the circuits and substrates that they may be mountedonto need not be as robust as the interconnections 30, but as will bediscussed in other embodiments later herein, a more robust substrate maynevertheless be desired. Ends of cell balancing circuits 32, 33, 35 areconnected to respective terminals of capacitors 12, 14, 16, 18. Eachcell balancing circuit 32, 33, 35 is also coupled by a connection to arespective series interconnection 30, as is illustrated in FIG. 1 a byan interconnection 31.

Although capacitors comprising terminals disposed at opposing ends areillustrated in FIG. 1 a, it is understood that capacitors 12, 14, 16, 18could comprise other geometries, for example, with terminals that extendfrom the same end of a capacitor. It is therefore understood thatalternative embodiments may utilize interconnections 30 and balancingcircuits 32, 33, 35 that are coupled in a different orientation to thatshown by FIG. 1 a, and that such orientation and implementation iswithin the scope of the present invention. Furthermore, although onlyfour series connected capacitors are illustrated in FIG. 1 a, the scopeof the embodiments and inventions described herein envisions theinterconnection of less or more than four series connected capacitors.

Referring now to FIG. 2, and other Figures as needed, there isillustrated a capacitor current vs. capacitor temperature graph, whereina series interconnection 30 between the terminals of two 2600 F |2.5V|60 mm×172 mm cylinder |525 g| capacitors is formed by of one .5″W×.125″ T×4.5″ L conductive bus bar interconnection. The uppermost curveillustrates that as capacitor current flow increases from 0 to about 275amps, about a 55 degree increase in capacitor temperature is observed.

Referring now to FIG. 3, and other Figures as needed, there are seeninterconnections provided with increased surface area. Those skilled inthe art will identify that as current through the capacitors 12, 14, 16,18 increases, the temperature of the capacitors and interconnections 30through which the current flows may increase. It has been identifiedthat a reduction in the capacitor temperature may be achieved throughthe coupling of a sufficiently sized thermally conductive heatdissipater material against the capacitor in a manner that sinks anddissipates heat away from the capacitor.

In one embodiment, it has been identified that interconnections 30themselves can act as a heat dissipater. In one embodiment, eachinterconnection 30 is configured to comprise one or more increasedsurface area portion 30 a. In the context of the present invention, whatis meant by increased surface area (as opposed to minimized) is anysurface geometry with which improved heat dissipation may be achieved.For example, if a flat surface were considered as a being minimized insurface area, any protrusion or depression would act to increase thesurface area. Hence, in one embodiment, a flat rectangular bus bar typeinterconnection may be replaced with one that is dimensioned to includeone or more ribbed portion 30 a that provides an increased surface areawith which additional heat may be drawn and dissipated away from thecapacitors 12, 14, 16, 18. It is understood that although described andshown as ribs, an increased surface area could be provided by othergeometries, for example, wings, posts, curved areas, surface roughening,and others known and used by those skilled in the art.

Referring back to FIG. 2, and other Figures as needed, there isillustrated by a middle curve that, for a given temperature, two seriesinterconnected 2600 F |2.5 V| 60 mm×172 mm cylinder |525 g| capacitorscan be operated at a higher current when connected in series by a busbar interconnection that comprises an increased surface area geometry.The middle curve illustrates that as capacitor current flow increasesfrom 0 to about 350 amps, about a 55 degree increase in capacitortemperature is observed. Series interconnections 30 between capacitors12, 14, 16, 18 may be thus configured with increased surface areas suchthat for a given temperature the current that series interconnectedcapacitors may be safely operated at may be increased. Similarly, seriesinterconnections 30 with increased surface areas facilitate that for agiven current, the operating temperature of a series interconnectedcapacitor may be reduced.

Referring again to FIG. 2, and other Figures as needed, there isillustrated by a bottommost curve, that at any given temperature, ascompared to the topmost curve and the middle curve, two series connected2600 F |2.5 V|60 mm×172 mm cylinder |525 g| capacitors can be operatedat a higher current when used with an external source of heat removal.The bottommost curve illustrates that as capacitor current flowincreases from 0 to about 475 amps, about a 55 degree increase incapacitor temperature is observed.

In one embodiment, an external source of heat removal comprises anairflow passing over and between the capacitors 12, 14, 16, 18, and theseries interconnections 30. The external source of heat removal can beused to further reduce the temperature of the capacitors 12, 14, 16, 18.By providing an external source of heat removal, series connectedcapacitors 12, 14, 16, 18 may be used at higher currents and/or lowertemperature in a wider range of applications and with greaterreliability, than without external heat removal. It is identified thatwhen an external source of heat removal is used with an interconnection30 that comprises an increased surface area, further heat reduction maybe achieved. Although identified as an airflow, other external sourcesof heat removal may also be used and are within the scope of the presentinvention. For example, external sources of heat removal may be providedby immersion in, or exposure to, liquid, fluid, gas, or other mediumcapable of safely acting to remove or dissipate heat away from theinterconnections 30 and/or capacitors 12, 14, 16, 18.

Referring now to FIG. 4, and other Figures as needed, there is seen acell balancing circuit 33 used with a circuit substrate. In oneembodiment, it is identified that each cell balancing circuit, forexample circuit 33, may be adapted to effectuate a further reduction inthe temperature of series interconnected capacitors, for example,capacitors 14, 16. In one embodiment, circuit 33 includes one or morecircuit substrate 33 b portion. In one embodiment, circuit substrate 33b may comprise a thermally conductive material. In one embodiment,circuit substrate 33 b may comprise a thermally and electricallyconductive material. In one embodiment, wherein the circuit substrate 33b is electrically conductive, cell-balancing circuit 33 may beinsulatively coupled to the circuit substrate 33 b, for example, by aninsulative portion 33 c disposed therebetween.

In one embodiment heat dissipation circuit substrate 33 b potion may bemade of two or more electrically separated portions 33 d, 33 e, and/or33 f. In one embodiment, cell balancing circuit 33 may be thermallycoupled to electrically separated portions 33 dand 33 e and to terminalsof capacitors 14 and 16, as follows: one portion of circuit 33 iscoupled to portion 33 d, and a second portion of circuit 33 is coupledto portion 33 e. In this manner, an appropriately selected circuitsubstrate 33 b material, for example aluminum, can be used to draw heataway from the capacitors 14 and 16 through the capacitor terminals ofcapacitors 33. In one embodiment, heat dissipation circuit substrate 33b may comprise one or more increased surface area portion, for example,one or more rib, or the like.

Those skilled in the art will identify that thermal and/or electricalconnection of the heat dissipation substrate 33 b to the cell balancingcircuit 33, as well as to terminals of capacitors 14 and 16, would needto be made in a manner so as to not interfere with the electricaloperation of the capacitors and the circuit. For example, for each cellbalancing circuit 33, physical contact to, and electrical insulationfrom, each heat dissipation substrate may be effectuated by use of aninsulated portion between circuit and the heat dissipation substrate. Itis understood that other thermal and electrical connections andadaptations could be made without undue experimentation, and would bewithin the scope of one skilled in the art.

Referring now to FIG. 5, and other Figures as needed, there is seen acapacitor housing configured to provide an increased surface area. It isidentified that a capacitor 55 housing may also be adapted to effectuatereduction of the temperature of the capacitor. For example, in oneembodiment, a capacitor 55 may comprise one or more increased surfacearea portion, for example, one or more rib 55 b, or the like. When usedin combination with other embodiments described herein, the increasedsurface area portions illustrated by FIG. 5 would allow for even moredissipation of heat away from the capacitor 55.

Referring now to FIG. 6, and other Figures as needed, there are seen ina top, end, and side view, six series interconnected capacitors.Although six series interconnected double-layer capacitors 81 arerepresented in FIG. 6, it is understood that the principles describedherein could be extended to fewer or more capacitors. For example,wherein 42 volts was a desired working voltage, a greater number ofdouble-layer capacitors may be connected in series; for example, sixteen2.5 volt rated capacitors could be connected in series.

As illustrated in FIG. 6, capacitors 81 are interconnected by bus bars30. In accordance with principles described herein, it is understoodthat in one embodiment, bus bars 30 may comprise one or more increasedsurface area portion (not shown in FIG. 6). In some embodiments, busbars 30 may comprise attachment points or holes whereat the bus bars maybe coupled to terminals of the capacitors by compression or expansionfittings, bolts, screws, or other fasteners as are known to thoseskilled in the art. Those skilled in the art will identify that if busbars 30 and/or terminals made of aluminum are used, a thin oxide layermay exist or be formed thereupon such that contact resistancetherebetween may be increased. It is identified that coupling of busbars 30 to terminals of capacitors 81 using fasteners may not providesufficient coupling force to break through the oxide and/or prevent itsformation thereafter. When current flows through an increased contactresistance, the temperature of the terminals may become increased. Asthe current is increased, for example, at the high currents thatdouble-layer capacitors are capable of being used at, the temperature ofthe terminals and, thus, the capacitors 81 could be increased evenfurther.

In one embodiment, better contact and lowered resistance path forcurrent flow and, thus, reduced heat generation, is achieved when busbars 30 are welded directly to respective terminals of capacitors 81. Asused herein, the term welding is intended to mean coupling of bus bars30 to terminals of capacitors to thereafter form an integral structurethat is made of the bus bars and terminals, and depending on weldingtechnique used, possibly an additional welding material. During theformation of the welded structures, it is identified that thesurface-to-surface contact and, thus, the increased resistance caused byoxide layers would be substantially reduced or eliminated. Welding canbe preferably effectuated by laser welding, ultrasonic welding, coldforming, or other welding techniques such as gas metal arc welding, gastungsten arc welding, shielded metal arc welding, brazing soldering,etc, as are known by those skilled in the art.

In one embodiment, prior to welding of bus bars 30 to respectiveterminals, capacitors 81 are placed into a holding fixture so as tomaintain the terminals of the capacitors in a fixed orientation andseparated by a desired fixed distance (illustrated as “×”). In oneembodiment, the desired fixed distance is the same or similar distanceas between bus bar 30 attachment points. By making the desired fixeddistance between the terminals the same as the distance between bus barattachment points, the bus bars 30 may be quickly and accurately alignedto the terminals of the capacitors during one or more manual orautomated weld step. In one embodiment, bus bar 30 attachment points maycomprise openings, voids or holes 82. In one embodiment, circular holes82 are sized to slideably fit over the outer diameter of capacitor 81terminals. In one embodiment, capacitor 81 terminals may be disposedthrough holes 82 in a manner such that the bus bars 30 and the terminalscan be easily accessed by welding apparatus from a direction external tothe structure capacitors 81. In one embodiment, after welding to thecapacitor 81 terminals, it is understood that a rigid or semi-rigidintegrally formed self-supporting structure comprised of bus bars 30 andthe capacitors is created.

Those skilled in the art will identify that welding to form an integralstructure not only reduces the formation of oxides and oxide layers, butas well, facilitates ease of manufacture. For example, it is identifiedthat the weld or weld like joints formed between the bus bars 30 and theterminals minimizes movement of the capacitors 81 and theirinterconnections relative to one another. Because after welding thestructure is self-supporting, movements that can degrade the physicaland electrical connections made between bus bars 30 and capacitors 81can be minimized thereafter. In one embedment, as compared to the priorart, it is identified that a self-contained self-supporting module ofcapacitors capable of dissipating heat generated by high currents can beprovided without necessarily needing to be fixidly mounted in, orencapsulated by, a protective housing. It is further identified thatwhen terminals of capacitors are axially disposed, welded bus bars 30can be used to provide structural stability at both a top and bottom ofthe resultant self-supporting structure, which may provide betterstability than when capacitors with radially disposed terminals at oneend (not shown) are used. In FIG. 6, one of five possible balancingcircuits 33 is represented by dashed lines. In one embodiment, inaccordance to principles described with FIG. 4, a circuit substrate 33 bportions of balancing circuits 33 could also be coupled to terminals ofcapacitors 81 by fasteners or, if desired, by welding. When welded, itis identified that the balancing circuits 33 could provide furtherstructural and electrical integrity to the resultant structure formed bythe bus bars 30 and the capacitors 81.

Referring now to FIG. 7, and other Figures as needed, there is seen atransparent view of a container and series interconnected capacitorstherein. In some embodiments, it may be desired to use a sealedcontainer 80 to encapsulate the capacitors 81 illustrated in FIG. 6. Inone embodiment, the sealed container 80 may be filled with an externalheat removal medium 85, for example, an oil or an alcohol. The externalheat removal medium can be used to facilitate the transfer of heat awayfrom the capacitors 81 and bus bars 30 to the walls of the container 80preferably without electrically or chemically affecting the performanceof the capacitors 81. It is identified, however, that dimensionalrequirements of the container 80 may limit the configuration andpotential use of some of the heat reduction principles and embodimentsdescribed previously herein and, thus, one or more of the featuresdescribed by previous embodiments may or may not be able to be fully oreven partially adapted for use within a sealed container 80. Forexample, in one embodiment, wherein there are six 2600 F |2.5 V|60mm×172 mm cylinder |525 g| capacitors interconnected by welded bus bars30 and cell balancing circuits (not shown), to effectuate fitment in thedesired dimensions of a container 80, one or more of the bus bars 30,cell balancing circuit substrates, and capacitors 81 may be configuredwith minimized or no increased surface area portions (i.e. flat orsmooth surface areas).

It is identified that bus bars 30 and the capacitor terminals they arewelded to preferably comprise materials that minimize well knownelectro-chemical and galvanic effects that can occur when dissimilarmetals are placed in contact with each other. Accordingly, similarmetals may be used for capacitor terminals 91 a, 92 b and bus bars 30and, possibly, as well, for the capacitor housing and lid. Thus, ifterminals 91 a, 92 a of respective capacitors 91, 92 are aluminum, inone embodiment the bus bars 30 are preferably also made of aluminum.

Prior to use of the welded bus bars 30 of the present invention, whenfasteners were used to connect bus bars to terminals, it was desiredthat the bus bars and fasteners maintain their geometrical structureunder pressure and/or high temperature, for example, as when a bus barwas forced against a terminal by a screw type fastener. Under highpressure connection forces, those skilled in the art will understandthat some bus bars could flow or change their shape, for example, ascould occur if bus bars comprised of common grade aluminum were used.Those skilled in the art will identify that over time a change in shapeor geometrical structure could increase the resistivity at aninterconnection point between a terminal and a bus bar, for example, byan increased spacing between a bus bar and terminal. To this end, withaluminum bus bars attached to aluminum terminals by fasteners,high-grade metal aluminum that does not flow or change its geometryeasily under pressure has been used. For example, in one embodiment, a4047 grade of aluminum, or other similar non-ductile high grade metal,is used when aluminum fastener type metals and interconnections areused. Those skilled in the art will identify that use of such high-grademetals, however, may result in higher manufacturing costs beingincurred.

With the welded bus bars of the present invention, because high-pressuretype fasteners and connections need not be used, high-grade metal busbars are not necessarily required. Because with the present inventionlower or common grade metal may be usable as a material for bus bars 30,as well, as for the terminals, housing, and the lid, a reduction in thecost of manufacture of double-layer capacitors, as well asinterconnected modules, made therefrom, may thus be possible.

A product comprising one or more double-layer capacitor 81interconnected by welded bus bars 30 may be provided for use in manydifferent applications. For example, one or more interconnectedcapacitor 81 may be used as a primary or secondary energy source for avehicle. Because the welded combination of double-layer capacitors 81and bus bars 30 may be used to create a structure that isself-supporting and self-contained, the capacitors 81 may be mounted inmany more physical orientations than previously possible. In oneembodiment, conventional batteries in a hybrid vehicle may be replacedby, or supplemented by such a structure as described herein. In contrastto typically used automotive batteries, because each individualcapacitor 81 housing is sealed, the capacitors may be mounted withoutuse of an encapsulating enclosure, as well as in many differentorientations, for example, up, down, sideways, etc.

While the particular systems and methods herein shown and described indetail are fully capable of attaining the above described object of thisinvention, it is understood that the description and drawings presentedherein represent some, but not all, embodiments of the invention and aretherefore representative of the subject matter which is broadlycontemplated by the present invention. For example other dimensions,other form factors, other types of capacitors and other energy storagedevices could be adapted and used with one or more principles disclosedherein. Thus, the present invention should be limited by nothing otherthan the appended claims and their legal equivalents.

1. A method of using a plurality of capacitors comprising: providing afirst and a second double-layer capacitor; providing a first bus bar;welding a first end of the first bus bar to the first double-layercapacitor to form a self-supporting structure; and welding a second endof the first bus bar to the second double-layer capacitor to form theself-supporting structure.
 2. The method of claim 1, further comprisingpassing a current of at least 250 amps through the first bus bar.
 3. Themethod of claim 1, further comprising: providing a third double-layercapacitor; providing a second bus bar; welding a first end of the secondbus bar to the third capacitor to form the self-supporting structure;and welding a second end of the bus bar to the second capacitor to formthe self-supporting structure.
 4. The method of claim 3, furthercomprising: providing an electrical device; and coupling thedouble-layer capacitors to the electrical device to pass current betweenthe capacitors and the electrical device.
 5. The method of claim 4,wherein the electrical device comprises a propulsion engine.
 6. Themethod of claim 1, wherein the first and second capacitors are connectedin series by the bus bar.
 7. The method of claim 1, wherein theself-supporting structures comprised of double-layer capacitors and busbars are oriented in any orientation.